The proposed experiments are designed to examine the two basic processes underlying binocular vision: fusion and stereopsis. By examining the various facets of human fusional response my aim is to arrive at a cohesive and comprehensive description of it. The results will provide information (1) on the way in which fusional information is assessed at the retinas within Panum's fusional areas, (2) the way in which disparity information is processed by the central pairing mechanism, (3) the relative roles the central and motor components play in the fusion and stereopsis, (4) the nature and extent of interactions between the two mechanisms.